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A wireless magnetic resonance energy transfer system for micro implantable medical sensors.

Li X, Zhang H, Peng F, Li Y, Yang T, Wang B, Fang D - Sensors (Basel) (2012)

Bottom Line: The energy transfer efficiency of the four-coil system is greatly improved compared to the conventional two-coil system.In addition, the output current varies with changes in the distance.The whole implanted part is packaged with PDMS of excellent biocompatibility and the volume of it is about 1 cm(3).

View Article: PubMed Central - PubMed

Affiliation: School of Electronics and Information Engineering, Beijing Jiaotong University, Beijing 100044, China. lixiuhan@bjtu.edu.cn

ABSTRACT
Based on the magnetic resonance coupling principle, in this paper a wireless energy transfer system is designed and implemented for the power supply of micro-implantable medical sensors. The entire system is composed of the in vitro part, including the energy transmitting circuit and resonant transmitter coils, and in vivo part, including the micro resonant receiver coils and signal shaping chip which includes the rectifier module and LDO voltage regulator module. Transmitter and receiver coils are wound by Litz wire, and the diameter of the receiver coils is just 1.9 cm. The energy transfer efficiency of the four-coil system is greatly improved compared to the conventional two-coil system. When the distance between the transmitter coils and the receiver coils is 1.5 cm, the transfer efficiency is 85% at the frequency of 742 kHz. The power transfer efficiency can be optimized by adding magnetic enhanced resonators. The receiving voltage signal is converted to a stable output voltage of 3.3 V and a current of 10 mA at the distance of 2 cm. In addition, the output current varies with changes in the distance. The whole implanted part is packaged with PDMS of excellent biocompatibility and the volume of it is about 1 cm(3).

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Related in: MedlinePlus

Schematic of the Class-E power amplifier and driving circuit.
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f5-sensors-12-10292: Schematic of the Class-E power amplifier and driving circuit.

Mentions: The schematic of Class-E power amplifier introduced in this paper is shown in Figure 5. The basic Class-E power amplifier circuit is composed of MOS switch, RF choke, a parallel capacitor (Cp), load network (LC) and load (RL) [22]. Parasitic capacitance of MOS drain increases Cp [23]. When analyzing the Class-E amplifier working principle, it is assumed that the on-resistance of MOS transistor is zero and the off-resistance of MOS transistor is infinite. Square wave is applied to the gate of MOSFET to control the MOS switch. When a high voltage is applied, the MOS switch is on and current flows through the MOSFET. The drain-to-source voltage is approximate zero. When a low voltage is applied, the MOS switch is off and the drain-to-source voltage equals to the voltage across Cp. Because the magnetic resonant coupling between the transmitter coils and receiver coils will reduce the resonant frequency of the system, a tuning capacitance (Cx) in series with LC is added to adjust the resonant frequency point of the transmitting circuit.


A wireless magnetic resonance energy transfer system for micro implantable medical sensors.

Li X, Zhang H, Peng F, Li Y, Yang T, Wang B, Fang D - Sensors (Basel) (2012)

Schematic of the Class-E power amplifier and driving circuit.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3472828&req=5

f5-sensors-12-10292: Schematic of the Class-E power amplifier and driving circuit.
Mentions: The schematic of Class-E power amplifier introduced in this paper is shown in Figure 5. The basic Class-E power amplifier circuit is composed of MOS switch, RF choke, a parallel capacitor (Cp), load network (LC) and load (RL) [22]. Parasitic capacitance of MOS drain increases Cp [23]. When analyzing the Class-E amplifier working principle, it is assumed that the on-resistance of MOS transistor is zero and the off-resistance of MOS transistor is infinite. Square wave is applied to the gate of MOSFET to control the MOS switch. When a high voltage is applied, the MOS switch is on and current flows through the MOSFET. The drain-to-source voltage is approximate zero. When a low voltage is applied, the MOS switch is off and the drain-to-source voltage equals to the voltage across Cp. Because the magnetic resonant coupling between the transmitter coils and receiver coils will reduce the resonant frequency of the system, a tuning capacitance (Cx) in series with LC is added to adjust the resonant frequency point of the transmitting circuit.

Bottom Line: The energy transfer efficiency of the four-coil system is greatly improved compared to the conventional two-coil system.In addition, the output current varies with changes in the distance.The whole implanted part is packaged with PDMS of excellent biocompatibility and the volume of it is about 1 cm(3).

View Article: PubMed Central - PubMed

Affiliation: School of Electronics and Information Engineering, Beijing Jiaotong University, Beijing 100044, China. lixiuhan@bjtu.edu.cn

ABSTRACT
Based on the magnetic resonance coupling principle, in this paper a wireless energy transfer system is designed and implemented for the power supply of micro-implantable medical sensors. The entire system is composed of the in vitro part, including the energy transmitting circuit and resonant transmitter coils, and in vivo part, including the micro resonant receiver coils and signal shaping chip which includes the rectifier module and LDO voltage regulator module. Transmitter and receiver coils are wound by Litz wire, and the diameter of the receiver coils is just 1.9 cm. The energy transfer efficiency of the four-coil system is greatly improved compared to the conventional two-coil system. When the distance between the transmitter coils and the receiver coils is 1.5 cm, the transfer efficiency is 85% at the frequency of 742 kHz. The power transfer efficiency can be optimized by adding magnetic enhanced resonators. The receiving voltage signal is converted to a stable output voltage of 3.3 V and a current of 10 mA at the distance of 2 cm. In addition, the output current varies with changes in the distance. The whole implanted part is packaged with PDMS of excellent biocompatibility and the volume of it is about 1 cm(3).

Show MeSH
Related in: MedlinePlus